Early to bed and early to rise, makes a man healthy, wealthy, and wise.

-- Ben Franklin

Go to bed earlier. When you wake up (under normal circumstances) you'll have had enough sleep. Take some time to learn what is a normal amount of sleep for you. If you discover it varies significantly from the "average" required amount of sleep, seek professional help.

Once you've determined how much sleep time your body demands, go to bed at a time that will give you that amount of sleep and wake you up at the time most convenient for you. At that point you can experiment with techniques to alter your sleep patterns (multiple shifts, naps, etc) that will help you improve your productivity.

But productivity isn't just for doing more tasks now. It's doing them at a sustainable pace over the long-term. Damaging your body in the quest for maximum productivity would make your whole life less productive, wouldn't it?

I've often read the most important factor in sleeping is not so much how long you sleep but at which point during the sleep cycle you wake up.

Ideally you should wake up during light sleep. In the picture above, REM and above, and stages 1 and 2 would be light sleep. Stages 3 and 4 would be deep sleep. Awakening from deep sleep can lead to sleep inertia (grogginess).

Going by that hypnogram, you can see there is a minimum amount of sleep you should get to avoid sleep inertia, but there isn't an ideal number of hours or minutes.

Each sleep cycle lasts about 90 minutes, and there are alarms you can buy that will only ring during light sleep.

Shouldn't everyone just sleep 8 hours to have maximum energy? There was a huge study by the American Cancer Society that found that those people who report that they sleep 8 hours have a higher mortality than those who report 6 or 7 hours.

Correlation and causation aren't easy to determine but the data suggests that 8 hours aren't a one-size-fits all solution. Different people seem to have different sleep needs. If you want to find the optimal sleep length for yourself you have to experiment with different schedules.

There are basically two ways to go about finding the optimal sleep length:

1. Listening to your body. Wake up without an alarm clock but by setting an intention to wake up at a certain point in time. Your body will take the amount of sleep that it needs.

2. Numerical. Tools like RescueTime provide you with a numerical rating of your productivity. If one sleep shedule gives you a higher productivity rating you have found your winner.

Is sleep length the only thing that matter? It isn't. Regular sleeping pattern beat unregular ones.

It's also beneficial when you don't directly awake from deep sleep phases. Unfortunately it isn't as easy as Louis suggests above. It's true sleep circle takes on average 90 minutes but that doesn't mean that there no variance.

How do you solve the problem? There are again two solutions:

1. Listening to your body. Don't use an alarm clock. You will naturally wake up when it's convenient for your body.
2. Use technical devices like the Zeo. The Zeo monitors your sleep phases and awakes you at the right moment.
3. Use audio brainwave entertainment to influence your sleep phases. iMusic Deep Sleep would be an example for such a product. (I'm not sure whether this approach works but it seems to make sense on first glance)